The present invention relates generally to connections between modular elements. More particularly, the present invention relates to connection assemblies which facilitate the connection of a module containing processing circuitry with a terminal block, such as a module of a digital protective relay and a terminal block connectable to a power distribution network.
In U.S. Pat. No. 5,999,394, a terminal block assembly for a protective relay is disclosed which advantageously provides a reliable connection between the protective relay and an associated power distribution network. The terminal block assembly provides greatly enhanced accessibility, and allows a wide variety of connection schemes between the circuitry of the protective relay and the terminal block.
When a wide variety of connection schemes are possible, such as when the relay processing circuitry consists of any combination of independent, separately removable and replaceable special purpose processing modules, it is desirable to ensure that the proper terminal block is connected to a proper relay processing module.
In the example of a protective relay having relay processing circuitry embodied by multiple replaceable modules, each of which connects to a terminal block, serious problems can result from a module being installed with an incorrect orientation (e.g., upside down), or being installed and connected to the wrong terminal block. These problems can range from damage to the module to physical harm to the installer or other associated with the power distribution network.
To aid in installing modules, one approach is to provide each module 10 with a card pull or ejector 12 (see FIG. 1) which are rotatably connected to the module. By applying pressure to the card pulls, the module can be inserted or removed more easily; more particularly, the module connectors can be urged past the shorting fingers of the terminal block. As described in Applicant""s U.S. Pat. No. 5,999,394, the terminal block has shorting fingers which, for safety purposes, are connected together in pairs when no module is connected to the terminal block, and are separated when a module is inserted. While the card pulls can be made of plastic, plastic does not typically provide sufficient strength for the card pulls. Thus, plastic card pulls tend to break in use. Card pulls can be made durable by using die cast metal; however, the strength of the metal card pulls can facilitate an improper connection, as the installer can easily provide sufficient force to break any alignment aids which may be contained at the rear of the module, on the terminal block, or within the relay cavity.
Accordingly, it would be desirable to provide a connection assembly for aligning and connecting processing circuitry, particularly that of a modular digital protective relay, and a properly-corresponding terminal block assembly.
The present invention overcomes the problems noted above, and achieves additional advantages, by providing for a connection assembly, and connection elements, for facilitating connection between a terminal block and a module containing processing circuitry. According to exemplary embodiments, the connection assembly can include a keycode plate and keycode connection elements. The keycode plate is molded to align with and fit over terminal block connection elements, the terminal block connection elements extending through openings provided in the keycode plate. The keycode elements at one end fit into slots provided in the keycode plate, and the keycode elements at another end fit into pre-existing recesses on a module cover. The recesses are provided in locations on the module or module cover so as to align with and receive corresponding keycode elements, thereby substantially ensuring the correct module is connected to a correct terminal block and that an incorrect module is substantially prevented from connection to an incorrect terminal block. Blocking elements can be placed at appropriate locations to prevent the connection of improperly matched modules and terminal blocks.
The assembly, keycode plate, and module cover of the present invention can substantially ensure proper alignment and mating of a relay processing module and a terminal block, or other similar components.